As the brain ages, it loses its ability to generate new cells, while existing cells lose functionality, including the ability to prevent inflammatory mediators in the blood from passing through the blood-brain barrier. At the same time the aged brain tends to produce higher levels of inflammatory agents such as leukotrienes, and loses some of its ability to counter the effects of inflammatory mediators, resulting in neuroinflammation and cognitive impairment. A major contributor to neuroinflammation are leukotrienes. There is evidence that leukotriene receptor antagonists, such as Montelukast sodium, have the potential to reduce neuroinflammation and restore brain cell function. Such treatments can be effective for treating various neurodegenerative diseases and conditions, including Huntington's disease, Parkinson's disease, loss of memory function, spinal cord and brain injuries, and stroke.
Montelukast sodium (MTL) is an orally active leukotriene receptor antagonist commonly used to treat patients suffering from chronic asthma as well as symptomatic relief of seasonal allergic rhinitis. During a normal respiratory inflammation response, the binding of cysteinyl leukotrienes to the leukotriene receptor induces inflammation within the respiratory pathway, generating asthmatic symptoms. MTL functions to suppress this inflammatory response by binding to the leukotriene receptor with high affinity and selectivity, thereby blocking the pathway leading to the physiological response for extended periods. Recently, neuroinflammation within the brain has been linked to age-related dementia and neurodegenerative diseases. MIL applied under these biological conditions has been shown to significantly reduce neuroinflammation, elevate hippocampal neurogenesis and improve learning and memory in old animals.
Presently, Montelukast sodium is marketed in a tablet form under the name of “Singulair®.” One of the greatest challenges for using MTL in a tablet form is the inconsistent bioavailability. Although MTL is freely soluble in water, its solubility is reduced under acidic conditions normally found in the stomach. This has led to relatively slow and inconsistent absorption into the blood stream, with maximum concentrations occurring only after 2-4 hours, thereby limiting its use to chronic applications rather than for rapid acute treatment. Experimental studies indicate that the major obstacles limiting MTL absorption pertain to its solubility, the rate of dissolution from the tablet platform and transport across biological membranes.
U.S. Pat. Nos. 8,575,194 and 9,149,472 disclose methods of improving cognitive impairments by administering a single tablet or capsule that comprises an extended release (ER) component and an immediate release (IR) component in a single dosage unit. The method involves administering the dosage unit to provide an initial burst of IR API into the system, followed by the ER API over the course of 12 hours, thereby maintaining a constant effective plasma level. Disclosed embodiments include a tablet with an ER core and an IR shell or a capsule containing a mixture of ER and IR beads combined in a specific ratio to achieve the desired effect. In an alternative embodiment, the regimen in general consists of an initial high dose of 10 mg of MTL followed by 5 mg doses approximately every 2 hours afterwards over the course of 12 hours. The patents discuss plasma levels as being critical for achieving cognitive improvement. However, MTL can only exert its therapeutic effects if it crosses the blood-brain barrier (BBB) and accumulates in the cerebrospinal fluid (CSF) at sufficient concentration levels. Neither plasma nor CSF concentration levels of MTL are discussed in the patents.